Generate a license key using RSA PSS for a customer

import * as wmill from "https://deno.land/x/[email protected]/mod.ts";

export async function main(client: string) {

  const encoded = new TextEncoder().encode(client);

  // key generated by https://hub.windmill.dev/scripts/helper/1509/generate-an-rsa-pss-key-pair-helper

  let privateKey = await importPrivateKey(

    (await wmill.getVariable("u/user/your_private_key"))!,

  );

  let signature = await crypto.subtle.sign(

    {

      name: "RSA-PSS",

      saltLength: 32,

    },

    privateKey,

    encoded,

  );

  // Combine the encoded data and signature to create a license key

  const licenseKey = `${btoa(client)}.${abToBase64(signature)}`;

  return licenseKey;

}

function abToBase64(arrayBuffer: ArrayBuffer) {

  return btoa(String.fromCharCode.apply(null, new Uint8Array(arrayBuffer)));

}

function importPrivateKey(pem: string) {

  const binaryDerString = window.atob(pem);

  const binaryDer = str2ab(binaryDerString);

  return window.crypto.subtle.importKey(

    "pkcs8",

    binaryDer,

    {

      name: "RSA-PSS",

      hash: "SHA-256",

    },

    true,

    ["sign"],

  );

}

function str2ab(str: string) {

  const buf = new ArrayBuffer(str.length);

  const bufView = new Uint8Array(buf);

  for (let i = 0, strLen = str.length; i < strLen; i++) {

    bufView[i] = str.charCodeAt(i);

  }

  return buf;

}